textproduct: Quad Cities

KEY MESSAGES

- Extreme Heat Warning continues through Thursday evening for much of the area with ongoing prolonged period of hot and very humid conditions. Daily peak heat index values of 100 to 110 and nighttime low temperatures only dropping into the mid to upper 70s.

- Humid conditions will continues into the holiday weekend. Cloud cover and slowly increasing storm chances will help to lower temperatures. Storms will have the potential to produce heavy rainfall

SHORT TERM /THROUGH WEDNESDAY/

Issued at 158 PM CDT Tue Jun 30 2026

Extreme heat and humidity will continue but all models are showing the gradual eastward shift to the heat dome. As it does, the nocturnal convection will move closer to the area.

Convection in the Plains is in a channel of moisture than has a tropical connection through west Texas and Mexico. Thus through the late afternoon and evening hours no rain is expected.

After midnight the question becomes will any nocturnal convection invade parts of the area. Most very short term models suggest no rain. The exception is the NAMNest which brings some nocturnal showers into the area after midnight. IF this solution is correct then areas in the Highway 20 corridor west of Dubuque 'might' see some rain. However, the overall probability is low at 15-25 percent.

Wednesday will be a repeat of Tuesday with extreme heat and humidity area-wide. However, with the previous nights convection being a bit closer, cloud cover may help to hold down temperatures a little. Heat indices still look to be in the 100 to 110 range with it being day three of the heat.

LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/

Issued at 158 PM CDT Tue Jun 30 2026

When storms do return to the area, high moisture levels in the atmosphere brings the risk of heavy rainfall.

Wednesday night through Friday night Assessment...a certainty (>98%) that humid conditions continue. Low (<25%) confidence regarding the timing of eventual convection.

Starting Wednesday night and continuing through Friday night the heat dome will gradually move toward the east coast and the upper ridge begins to flatten. As it does, disturbances moving around the edge of the heat dome will bring the potential for storms. However, each round of storms will influence where the subsequent round of storms will initiate and eventually move.

Wednesday evening has a high (>80%) probability of being dry across the area. Nocturnal storms late Wednesday night into Thursday morning look to impact areas north of Highway 30. Residual cloud cover from the nocturnal convection and expected new convection Thursday afternoon will likely temper temperatures and may hold heat indices in the 95 to 100 range. However, if the convection is further north than expected then heat indices may again exceed 100.

The expected convection Thursday night into Friday has the potential to be more interesting.

The heat dome will have moved further to the east and there is a respectable upper level disturbance progged to move out of the Rockies and toward the Midwest. The signals are there for a storm complex to develop in the Plains that moves east overnight. The complex will be in a weakening phase as it arrives in eastern Iowa in the pre-dawn hours but may be capable of some isolated severe storms. If severe storms would occur, damaging winds would be the primary risk.

Boundaries and cloud cover left over from the Thursday night storms will help to hold down temperatures and also provide boundaries for diurnal convection Friday afternoon that will continue into Friday night.

Prior to Friday, areal coverage of any storms will be low (15-30%). Starting Friday, chances will increase to 30-50% but not all areas will see rain.

Saturday through Tuesday Assessment...a certainty (>95%) that humid conditions will continue. Low (20-30%) confidence on storm timing and areal coverage.

Another disturbance moving through the Midwest Saturday and Saturday night currently looks to have the better chances to produce rain. This may or may not be in the form of an organized storm complex. Right now, the model consensus has rain chances at 30-55% with the better chances along/north of I-80.

Starting Sunday, there are additional upper level disturbance progged to move through the area each day. However, there are timing differences. The main message is that while there are rain chances each day, not everyone will see rain. Additionally, areal coverage of any rain is low at 15 to 25 percent.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1213 PM CDT Tue Jun 30 2026

Density altitudes of 3 kft or higher will be seen through 02z/01. After 02z/01 the very short term models suggest the potential of LLWS across eastern Iowa and northern Illinois. Closer examination of forecast soundings indicate a very marginal LLWS of 25 knots in the 1.5-2.0 kft AGL layer and thus was not included in the 18z TAFs. After 16z/01 density altitudes will again increase to or exceed 3 kft.

DVN WATCHES/WARNINGS/ADVISORIES

IA...Extreme Heat Warning until 10 PM CDT Wednesday for IAZ040>042- 051>054. Extreme Heat Warning until 10 PM CDT Thursday for IAZ063>068- 076>078-087>089-098-099. IL...Extreme Heat Warning until 10 PM CDT Wednesday for ILZ001-002- 007. Extreme Heat Warning until 10 PM CDT Thursday for ILZ009- 015>018-024>026-034-035. MO...Extreme Heat Warning until 10 PM CDT Thursday for MOZ009-010.